Stories & Features

Jul 31, 2017

500 pounds of beef & 50 years: A look at Duncan Dam

Show captionPremier W.A.C. Bennett unveils a 30-ton stone monument at Duncan Dam in August, 1967, as a tribute to the 450 workers who built the facility a year ahead of time without a single loss of life.

Show captionA massive amount of water cascades through diversion tunnels at the Duncan Dam.

Show captionThe earth-filled Duncan Dam serves as a storage dam for flood protection downstream and to help maintain water flows for hydroelectric production in winter.

Show captionIt took less than four months after closing of the gates at the new Duncan Dam for water to fill the 45-kilometre-long Duncan Reservoir by July 1967.

Show captionLocated in a picturesque part of the province at the head of Kootenay Lake, Duncan Dam was the first BC Hydro dam completed in either the Columbia or Peace River systems.

Dam was the first finished by BC Hydro on Columbia or Peace River systems

Surrounding scenery aside, Duncan Dam lacks the wow factor of BC Hydro's massive hydroelectric dams. But as it turns 50 on July 31, 2017, the storage dam on the Kootenay River still has bragging rights in one key area: it was the first dam built by BC Hydro in either the Peace or Columbia river systems.

And because the dam at the head of Kootenay Lake was built as part of the Columbia River Treaty, way back in 1967, its history offers a window into a dramatically different era of B.C. history. When's the last time the public was invited to a project dedication party in which the main contractor served up 500 pounds of barbecue beef, 1,800 buns, and 100 pounds of weiners, free to the public?

That's what happened on August 17, 1967, a blazing hot 32°C day (known as 90° Fahrenheit back then) on which Premier W.A.C. Bennett unveiled a 30-ton stone monument at the dam as a tribute to the 450 men who engineered and built the structure in record time, nearly a year ahead of schedule and without loss of life.

That early completion of the dam, which took just two years to build, earned BC Hydro an extra $4 million in payments for downstream benefits and flood control as part of the Columbia River Treaty. But construction didn't come without adventure, or a bit of experimentation.

Dam's foundation was like a sponge

The men who worked underground to fill holes in the earth-fill dam reportedly worked for the union wage of $2.89 an hour. They helped construct a dam that was described – in the book Voices From Two Rivers – as "a heavy giant that has lain down on its back in the river, planting its head on the upstream end, extending its arms to reach above its head, its chest jutting up and legs pointing downstream."

A 25-metre waterproof underground wall was designed to control seepage of water under the dam and endured a hiccup when, during excavation, it collapsed amid the high spring runoff of 1976. And the strategy for ensuring the dam's soil compacted and settled was a combination of traditional engineering and new monitoring technologies.

Project manager Ed Quirk memorably told the Arrow Lakes News that the dam's foundation was like a sponge. "As you lay on it, you squeeze water out of it until as the time goes on it sets uniformly," he told the newspaper.

"The engineers decided it [settlement of the dam] was occurring better than anticipated," construction management engineer Bill Rea says in Two Rivers. "They plotted a logarithmic curve for the settlement against time and decided they could accelerate it. They changed the design of the core a little in [one] area, mixing it with more granular materials, so it was more flexible and self-healing, and let it settle."

At 40 metres high the dam may be small in comparison to the tallest of the dams in the Columbia River system: Mica Dam, at 240 m. But it has an outsized role in the Columbia River Treaty.

This map shows BC Hydro's dams on the Columbia River system.

Dam's role is storage, not generation

Located just north of Kootenay Lake at the confluence of the Duncan and Lardeau Rivers, Duncan Dam was designed to collect heavy spring runoff to prevent flooding downstream and to help maintain the flow of the Columbia – the Kootenay River feeds the Columbia as a tributary – for electricity production in the winter.

Due to its earlier-than-expected completion, the gates of the Duncan Dam were first closed on April, 1967. The reservoir filled to reach full pool by the end of July of that year, creating the 45-kilometre long Duncan Reservoir.

There are no power generation facilities at Duncan Dam, which stores water for the Kootenay Canal and Kootenay Canal and Corra Linn hydroelectric dams on the Kootenay River about midway between Nelson and Castlegar, and for Montana's Libby Dam, located way south on the Kootenai River.

Water levels for the Kootenay Canal are regulated by Duncan and Libby dams. The mouth (or head) of the canal is located at the south side of Fortis' Corra Linn Dam, with water also regulated under an agreement to ensure that Corra Linn and other dams on the Kootenay River – including the City of Nelson's Bonneville Falls Dam – have enough water for continued power production.

Columbia River Treaty & Duncan Dam

Our operations in the Columbia Basin are driven largely by the terms of the Columbia River Treaty, which was ratified by the U.S. and Canada in 1964. It resulted in the construction of three dams in B.C. for flood control and to increase the potential for hydroelectric power generation in both countries. The treaty also provided for the construction of Montana's Libby Dam, which created the Koocanusa Reservoir that crosses the Canada-U.S. border.

Between 1964 and 1973, BC Hydro built Mica, Duncan and Hugh L. Keenleyside dams. In return, the U.S. paid Canada $274.8 million on October 1, 1964, as well as additional amounts upon completion of each dam – totalling $69.6 million. And today the Columbia River dams – including Revelstoke, completed in 1984 – remain key facilities that produce nearly half of the electricity generated each year by BC Hydro.

Either Canada or the U.S. can terminate the treaty any time after September 16, 2024, provided 10 years' notice is given. As both countries work on modernizing the treaty, The Province of British Columbia has consulted closely with Columbia Basin residents through the Columbia Basin Trust.

The Columbia River Treaty is considered by many to be among the most successful trans-boundary water treaties in the world. But First Nations groups on both sides of the border, overlooked in original treaty negotiations, are now very much involved in cross-border consultations on treaty renewal. One priority for First Nations is the future of salmon on the Columbia, as salmon passage to Canada via the Columbia ended more than two decades before the treaty with the construction of the Grand Coulee Dam in Washington State in 1941.

BC Hydro continues to manage the environmental impacts of dam construction through the Fish and Wildlife Compensation Program that funds programs each year to benefit fish, wildlife, and their habitat.